1. Field of Use
This invention relates generally to automotive vehicles having multiple power demand functions such as vehicle propulsion and various auxiliary powered equipment. More particularly, but not exclusively, this invention relates to construction machinery vehicles commonly known as loaders, scrapers, dozers, graders, and machines which have relatively great auxiliary power requirements for operating associated implements, tools, or other vehicle and engine support equipment. The invention is particularly adaptable to vehicles in which the power source is a free-turbine-type gas turbine engine having torque multiplication characteristics and other power sources in which the output is through fluid torque converters as well as power sources which have relatively high torque backup characteristics.
2. Description of the Prior Art
Auxiliary equipment power-take-off generally known in the present day construction machinery vehicle art are usually associated with, and driven by, a rotating housing fluid torque converter having a power-take-off speed exactly in proportion to engine speed at any load condition. One serious problem associated with this arrangement is that under heavy propulsion power requirements, to as much as converter stall, the vehicle engine speed is reduced appreciably lower than that under light propulsion power requirements. This reduced speed has a noticeable adverse effect on the performance of the auxiliary powered or work performing implements. For example, a loader vehicle equipped with a material handling bucket requires high tractive effort, or propulsion, to force the bucket into a bank of material when, simultaneously, the auxiliary powered equipment, such as a hydraulic pump driven by the power-take-off, is transferring power to raise the bucket through the bank of material. During the operating cycle vehicle forward motion may be stalled, or nearly so, resulting in reduced engine speed and, therefore, reduced power output of the hydraulic pump resulting in a slower than desired raising of the bucket.
Other solutions to overcome inadequacy of power-take-off arrangements have been proposed such as represented in U.S. Pat. No. 2,842,273 wherein engine power output is divided by a planetary gear assembly. Prior art pertaining to gas turbine engine powered vehicles is notably limited particularly with regard to applications utilizing the torque multiplying characteristics of free-turbine-type gas turbine engines. This type of engine either has no mechanical connection between the compressor shaft and the power turbine shaft or is sometimes provided with a mechanical connection such as a slipping clutch with modulating control. Power available for auxiliary equipment from the engine compressor shaft, in either configuration, is limited. The power requirements of the auxiliary equipment reduces the compressor speed thereby reducing air intake and resulting in a serious adverse effect on engine performance. The limited auxiliary power output capability of the compressor shaft is sufficient for some gas turbine engine applications but is insufficient for most construction machinery. In addition, attempts have been made to power construction machinery vehicles by gas turbine engines simply by replacing the diesel engine and retaining the conventional fluid torque converter and auxiliary power-take-off. Such modification does not take advantage of the torque multiplying characteristic of the free-turbine-type engine design, in expensive and still suffers the same disadvantages of reduced engine speed and lower horsepower output at converter stall as a diesel engine with torque converter.